1. Field of the Invention
This invention relates to an accumulator or receiver dryer and a method of making the same, for use in an automobile air conditioning system. More particularly, the present invention relates to packaging replaceable desiccant in an accumulator or receiver dryer.
2. Description of the Prior Art
In air conditioning systems, and particularly those for automotive applications, the accumulator is typically located at the outlet end of the evaporator. Its purpose is to filter out any particulates in the refrigerant fluid and remove any moisture present in the refrigerant vapor. A desiccant material is placed within the accumulator housing specifically for the purpose of removing the unwanted moisture from the refrigerant vapor.
During assembly of the accumulator, it is important to avoid saturating the desiccant material. Handling the desiccant material during the assembly process introduces the potential for saturation from exposure to humidity of air in the assembly area. Therefore, handling should be kept to a minimum.
A fully sealed unitary housing is a desirable feature of an accumulator. A one-piece construction without joints that may leak is an objective of accumulator assemblies. The simplicity of a unitary housing is also an important feature, which reduces costs and improves reliability. Such a unitary housing can be accomplished by spin welding closed the accumulator housing as taught by U.S. Pat. No. 4,675,971 to Masserang.
In known accumulator assemblies and methods of making same, the desiccant material is added to the housing prior to welding and leak testing the accumulator assembly. This known method introduces the risk of saturating the desiccant, and results in a high scrap rate and material cost for damage the desiccant bag incurs during brazing and testing operations.
In addition, with known devices and methods of making these devices, field repair and rework are not practical. Repairs consist of removing the defective device and replacing the entire accumulator or receiver unit.
There are accumulators for air-conditioning systems which sealingly connect a separate desiccant container in the bottom of the accumulator housing prior to permanently assembling the accumulator. The desiccant remains serviceable through the bottom of the housing. This system is disclosed in U.S. Pat. Nos. 4,276,756 and 4,291,548 to Livesay.
The Livesay references disclose an access opening in the bottom of the housing that opens into the interior of a desiccant container. A separate, empty desiccant container is placed inside the accumulator housing. A U-shaped tube is placed inside the housing. The empty desiccant container is received in the bight portion of the U-shaped tube.
The desiccant container has an open lower end that communicates with the opening in the bottom of the housing. An annular seal attachment sealingly attaches the lower end of the desiccant container through the open lower end thereof. A detachable closure cooperates with the closure fitting to close the access opening in the housing. The desiccant container is filled after the housing has been permanently assembled by inverting the container and gravity feeding desiccant material. U.S. Pat. No. 4,291,548 discloses a desiccant container that is a foldable bag that can be inserted through the opening in the bottom of the housing.
U.S. Pat. No. 4,838,040 to Freeman discloses a receiver dryer in which the housing has a readily openable lid held in place by quick disconnect clamps. The lid can be removed to allow a desiccant canister to be inserted inside the housing. To ensure adequate sealing, the housing has an annular O-ring. The separate lid has an overhang that seals against the O-ring of the housing. Additionally, the lid has an internally depending sleeve segment that is provided with another O-ring. The two O-rings are necessary to completely seal the housing against leakage. The lid is secured in place by a quick disconnect clamping band.
Accumulators must maintain high standards during testing. Therefore, a one-piece or unitary design is desired for the housing. The number of access openings and weld joints should be kept to a minimum for the housing to withstand the demanding impact, leak and burst test requirements. A drawback associated with prior art arrangements that provide access to the desiccant material is the need for a separate access opening. Additional openings disrupt the integrity of the accumulator or receiver dryer housing. Any opening in the housing introduces the potential for leaks, so a minimum number of openings is desirable.
A leak proof housing can be manufactured by spin welding a unitary housing into a closed configuration. Therefore, the number of components and attachments inside the accumulator housing should be kept to a minimum to reduce the risk of components breaking loose during the spin weld process. The accumulator disclosed in Livesay and the receiver dryer disclosed in Freeman require several additional components to accomplish accessibility to the desiccant material making spin welding impractical. In addition, if the devices disclosed by Livesay or Freeman cannot be closed by spin welding without defeating their innovative design feature of a separate opening to provide access to the desiccant.
In Livesay, not only is an additional opening required, but a separate desiccant container to hold the desiccant material is necessary. A sealing attachment between the container and the housing is necessary to maintain the desiccant container's position within the housing, and a closure member is necessary to prevent desiccant material from escaping the container.
The receiver dryer disclosed by Freeman also requires significant additional structure. A separate lid, two O-rings, a clamping band and a separate desiccant container are all necessary additional components for access to the desiccant material. Additionally, the sealing attachment between the desiccant container and the casing disclosed by Freeman must be extremely reliable to avoid desiccant material from escaping the desiccant container and contaminating the interior of the casing.
The location of the desiccant within the housing is an important aspect of an accumulator design. Ideally, the desiccant is located near the top of the housing. Locating the desiccant near the top of the housing ensures all vapor components of the refrigerant pass through the desiccant thereby improving the accumulator's performance.
In operation, the liquid refrigerant settles in the bottom of the accumulator housing. Positioning the desiccant in the bottom of the housing introduces the risk of saturating the desiccant material. In addition, all of the vapor inside the accumulator housing is not forced through the desiccant. The vapor that remains near the top of the housing never reaches the desiccant material and may contain unwanted moisture as a result. The Livesay references disclose locating the desiccant in the bottom of the housing, which is not desirable for optimum accumulator performance.
What is needed is an accumulator housing that can be accessed for inserting or removing desiccant material, having a minimum of components and without separate access openings that compromise the integrity of the housing.